Multivibrator



Jan. 28, 1930. 1 B. VAN DER POL 1,744,935

MULT I VI BRAT 0R Filed Jan. 11. 1927' INVENTOR THASAR VAN an 9:

BY A TORNEY Patented Jan. 28, 1930 UNITED STATES PATENT? OFFICEBALTEASAR VAN DER POL, OF EINDHOVEN, NETHERLANDS, ASSIGNOR TO THE RADIOCORIPORATION OF AMERICA, A CORPORATION OF NEW YORK MULTIVIBRATORApplication filed January 11, 1927, Serial No. 160,507, and in theNetherlands January 12, 1928.

The present invention has referenceto a so-called multi-vibratorcircuit-arrangement. In its original form such arrangement consistsessentially of an even number of triodes mutually coupled in resistanceamplifying circuits, the anode of the last triode being coupledretroactively to the grid of the first one. Such system in its simplestarrangement (comprising but two triodes) is diagrammatically shown inFigure 1 of the accompanying drawing. Intense current impulsesperiodically occur in these systems, the frequency of said impulsesbeing determined by the values of C and R.

According to the invention the same results are reached with half thenumber of thermionic apparatus, provided the triodes are replaced bytetrodes (doublegrid valves), between the two grids of which theperiodically discharged condenser is interposed, one of said two gridsbeing connected to the cathode across the leak resistance.

An electrical-scheme of an embodiment of the invention is shown inFigure 2.

In a discharge tube are sealed an anode A, a filament F and between themtwo grids G and G The filament F is supplied from a battery B and thecurrent in the anode circuit is supplied by a battery B and if desired,by a battery B connected in series therewith. The point P of the anodecircuit is connected directly to the grid G and with the interpositionof a condenser C (which may be adjustable or not) to the other grid GThe latter grid is finally connected through a leak resistance R to thefilament. The value of the condenser C should be, for example, between2000 centimeters and 1 microfarad, the resistance 7* being at this pointsome thousands of ohms and the resistance R being about 1 megohm.

In such a system periodic current impulses are maintained, which areaudible, for example, in a telephone or other receiving apparatus T inthe anode circuit. This phenomenon may briefly be explained somewhat asfollows: During each impulse the condenser C is discharged and in thereverse sense recharged at a very high starting speed which, however,gradually decreases until again a discharge occurs but by this time inthe reverse sense. The low selfinduction present in the connecting wiresmaintains the phenomenon in somewhat the same manner as that in whichtoo small a flywheel maintains the operation of a piston-machine havingtwo dead points. The smaller the said selfinduction, the more differentfrom the sine-shape will be the current curve of the discharges and themore easily it will be possible, if so desired, to sift out very highharmonics. Thus, it is, for example, possible to generateradiofrequencies in a high frequency circuit coupled across a highfrequency transformer to the anode circuit, the oscillations generatedin the anode circuit being comprised within the audible region.

What I claim is:

1. A multivibrator comprising a multi electrode space discharge deviceincluding two grids, a cathode, and a plate electrode. a condensercoupling the grids, a leak resist ance connecting one of said grids tothe oathode, and the other grid being connected to the cathode through asource of high potential, and a connectionbetween the plate and saidsource of high potential.

2. A multivibrator comprising a tetrode having two grids, a cathode, anda plate electrode, a condenser coupling the grids, a leak resistanceconnecting one of said grids to the cathode, a source of high potentialconnected to the plate, and a resistance connect- .ing the other of saidgrids to the source of high potential.

3. A multivibrator comprising a tetrode having two grids, a cathode, anda plate electrode, a condenser coupling the grids, a leak resistanceconnecting the grid located adjacent to the plate, to the cathode, and asource of high otential connected to the other of, said gri s and theplate.

4. A multivibrator comprising a multielectrode space discharge deviceincluding two grids, a cathode, and a plate electrode, a condensercoupling the grids, a leak resistance connecting one of said grids tothe cathode, and the other grid having a potential approaching that ofthe plate, and a source of potential connected to the plate.

In testimon whereof I aflix my signature, at the city 0 Eindhoven, this13th day of December, 1926.

BALTHASAR VAN DER POL.

